Run commands simply, with detailed diagnostics

Calling Perl's in-built "system()" function is easy, determining if it was
successful is *hard*. Let's face it, $? isn't the nicest variable in the
world to play with, and even if you *do* check it, producing a
well-formatted error string takes a lot of work.
"IPC::System::Simple" takes the hard work out of calling external
commands.